1. Field of the Invention
The present invention relates generally to thoracoscopic methods for performing cardiac procedures. More particularly, the present invention relates to thoracoscopic methods for performing procedures externally on or internally within the heart while the patient""s chest is unopened, the patient""s heart is stopped, and the patient is supported by cardiopulmonary bypass.
Coronary artery disease remains the leading cause of morbidity and mortality in Western societies. Coronary artery disease is manifested in a number of ways. For example, disease of the coronary arteries can lead to insufficient blood flow resulting in the discomfort and risks of angina and ischemia. In severe cases, acute blockage of coronary blood flow can result in myocardial infarction, leading to immediate death or damage to the myocardial tissue.
A number of approaches have been developed for treating coronary artery disease. In less severe cases, it is often sufficient to treat the symptoms with pharmaceuticals and lifestyle modification to lessen the underlying causes of disease. In more severe cases, the coronary blockage(s) can often be treated endovascularly using techniques such as balloon angioplasty, atherectomy, laser ablation, stents, hot tip probes, and the like.
In cases where pharmaceutical treatment and/or endovascular approaches have failed or are likely to fail, it is often necessary to perform a coronary artery bypass graft procedure using open surgical techniques. Such techniques require that the patient""s sternum be opened and the chest be spread apart to provide access to the heart. A source of arterial blood is then connected to a coronary artery downstream from an occlusion while the patient is maintained under cardioplegia and is supported by cardiopulmonary bypass. The source of blood is often the left or right internal mammary artery, and the target coronary artery can be the left anterior descending artery or any other coronary artery which might be narrowed or occluded.
While very effective in many cases, the use of open surgery to perform coronary artery bypass grafting is highly traumatic to the patient. The procedure requires immediate postoperative care in an intensive care unit, a total period of hospitalization of seven to ten days, and a recovery period that can be as long as six to eight weeks.
It would therefore be desirable to provide other, less traumatic methods and techniques for performing coronary artery bypass grafting. It would be particularly desirable if such techniques did not require opening of the patient""s sternum, and might be even more desirable if such techniques could be performed using thoracoscopic methods. Such thoracoscopic methods could decrease morbidity and mortality, cost, and recovery time when compared to conventional open surgical coronary bypass procedures. In addition, such methods could be even more efficacious than open-surgical bypass procedures.
2. Description of the Background Art
Conventional thoracoscopic techniques are described in Landreneau et al. (1992) Ann. Thorac. Surg. 54:800-807. Conventional open surgical procedures for performing coronary artery bypass grafting are described in Kirklin and Barratt Boyes, Cardiac Surgery, John Wiley and Sons, Inc. New York, 1993 (2nd Ed.). Copending application Ser. No. 07/730,599, assigned to the assignee of the present application, describes a catheter which is insertable into a patient""s arterial system and includes a distal balloon which can be expanded to occlude the ascending aorta. The coronary ostia remain unblocked so that the heart and proximal ascending aorta may be isolated while the patient is on cardiopulmonary bypass. This catheter is particularly intended to be used in heart valve replacement procedures.
According to the present invention, a method for closed-chest cardiac surgical intervention relies on viewing the region of the heart through a percutaneously positioned viewing scope, such as a thoracoscope. The patient""s arterial system will be partitioned during such interventional procedures at a location within the ascending aorta between the brachiocephalic artery and the coronary ostia. In a preferred embodiment, such partitioning is achieved by endovascularly advancing the distal end of a catheter to the desired location with the ascending aorta and expanding a blocking element on the catheter at said location to inhibit the flow of blood and other fluids past said location. Such partitioning facilitates isolation of the heart, and in particular permits the heart to be stopped while the patient is supported by cardiopulmonary bypass. Once the patient""s heart is stopped, a variety of surgical procedures can be performed using percutaneously introduced instruments in a minimally invasive fashion.
The methods of the present invention will be particularly useful for forming coronary artery bypass grafts in a patient suffering from coronary artery disease. The methods will be performed while the treating physician views the region of the heart through the viewing scope, with initial portions of the procedures being performed while normal heart function is maintained. As a first step, the physician will prepare an arterial blood source, typically by harvesting an internal mammary artery or other suitable artery. Conveniently, the lung beneath the internal mammary artery will be collapsed while the other lung remains ventilated. After the arterial blood source is prepared, cardiopulmonary bypass will be established, the patient""s arterial system will be partitioned, and the heart stopped, typically by introducing cardioplegic fluid to the isolated heart. A target location on the coronary artery will then be prepared to receive attachment of the arterial blood source, typically by forming an incision at a location downstream from a narrowed region in the artery. The arterial blood source can be connected to the coronary artery by various conventional anastomotic techniques, such as suturing.
The methods of the present invention provide a minimally-invasive approach for forming coronary artery bypass grafts with an efficacy equal to or greater than conventional open surgical bypass techniques. The methods of the present invention can be adapted to create anastomoses of a variety and type similar to those created by open surgical techniques, while greatly reducing patient trauma since there is no need to perform a sternotomy. Moreover, the preferred use of an endovascular catheter to partition the aorta and isolate the heart offers a substantial advantage over open surgical techniques where external clamps are placed on the aorta. External clamps can damage the aorta and may frequently cause the release of emboli from the aortic lumen. Additionally, since the sternum does not need to heal after the procedure, both internal mammary arteries can frequently be used in a single procedure to provide multiple bypass routes. Heretofore, one internal mammary artery was often left in place to provide blood flow to promote healing of the sternum in many open-surgical procedures.